1. Field of the Invention
This invention relates to devices for providing an electrostatic charge to particles and in particular relates to a device for electrostatically charging a flow of a sorbent or particulate matter for injection into a polluted gas stream to create a highly charged field therein causing the pollution particulates to become charged by contact with and adhere to the charged and sorbent particles and agglomerize together for passage to a granular filter wherein the sorbent and pollution particles with adhering materials are captured by the granular material of the filter, cleaning the gas flow.
2. Prior Art
Devices for charging particles are, of course, not new, and electrostatic guns for introducing electrostatically charge sorbent particles into a gas stream so as to create a large charged surface area therein that induce charging of the particulate matter contained in a polluted gas flow have heretofore been available. Examples of such electrostatic gun and antenna devices are shown, for example, in U.S. Patents to Schuff; U.S. Pat. No. 4,220,478; and to Schuff, U.S. Pat. No. 4,290,786, and as set out in earlier U.S. Patent Applications of the inventors identified as "Apparatus For Removing Particulate Matter and Gasses From a Polluted Gas Stream" filed Jun. 14, 1993, and a method set out in a U.S. patent of the inventors entitled "Method for Removing Particulate Matter and Gasses From a Polluted Gas Stream" filed Jun. 18, 1 993.
Only in recent years have air pollution control apparatus and methods been developed, like those set out above, that provide for the efficient and effective removal of fine particulate matter, particularly submicron size particles of pollution. Even with such earlier particulate removal systems substantial difficulties have been experienced, due to a lack of system versatility as, for example, when such systems were required to meet strict pollution removal requirements as have been imposed by governmental agencies for the removal of such particulate matter. In particular, such systems have lacked versatility to alter sorbent injection flows and sorbent particulate charging for different gas stream pollution states, which versatility is now provided by the system of the invention.
Like the earlier Schuff patents, the present invention involves an improved charging gun for imparting an electrostatic charge into a flow of sorbent materials. Unique therefrom, however, the invention provides an electrostatic charging gun that receives a supply voltage that can be varied according to the volume and type of the sorbent particulates injection into the polluted gas stream, so as to provide a maximum surface charge onto each sorbent particle. The sorbent particles, that all bear the same charge, will repel one another and are accordingly rapidly dispersed through the gas stream. This creates a large charged surface area, that, in turn, induces a maximum charging of the particulate matter within that gas stream. This charging tends to agglomerate the submicron and larger particulates, with the gaseous pollutants chemically reacting with the charged sorbent particles and with the particles in a media materials bed.
The above set out capability to vary the charging of the electrostatic gun of the invention is provided to accommodate a capability for varying the flow rate of sorbent particles injected into the polluted gas stream. Which flow rate variability is to provide for a sufficient volume of charged sorbent particulates in the gas stream to completely react with the volume of pollutants, both particulate and gaseous, as are present in a particular polluted gas stream. The ability to select a particular volume of sorbent particles passed from a hopper system of the invention provides for a sorbent presence to effectively react with all the pollutants as are actually present in the gas stream. Such reaction provides for agglomerizing those particles and sorbent particles, with the selected sorbent particles also chemically reacting with the gaseous pollutant submicron size particles, the agglomerized and reacted particles then removed by passage through an arrangement of moving and static media material beds.
The gas flow containing agglomerated particulates and sorbent particles with captured pollutants is passed to a series of moving and static media bed arrangements that provide for the removal and collection of the sorbent reacted products, particulates and pollution gases from the gas stream, cleaning that gas stream that is then vented to atmosphere. The above cited Schuff apparatus and method patents are examples of the state of prior art, but presented limited capacity for particulate removal from high volume polluted gas flows. The present invention overcomes these deficiencies by including a capacity for controlling the volume of sorbent material flow and for adjusting electrostatic charging of that material. A closely controlled volume of highly charged sorbent particles is thereby provided for completely reacting with all the particulate and gaseous pollutants are present in a specific polluted gas stream.